Having no natural enemies here to control it, the aphid expanded its range by more than 300 kilometers a year for the next two years, showing up in soybean fields from the Dakotas to Virginia and causing crop losses of more than $2.2 billion.
How did it get here? Probably it was carried in accidentally, says Sonny Ramaswamy, Kansas State University entomology department head. But, in this day and age, scientists have to consider that a new plant pathogen like this could be a deliberate introduction.
He sees the aphid invasion as a training exercise for scientists to prepare for an agroterrorist strike that pits a foreign insect pest against U.S. crops.
"There are interesting commonalities between how insects spread and how pathogens spread," he said. "In fact, insects, including this aphid, are natural carriers and vectors of a lot of plant pathogens." The soybean aphid colonizes soybeans, but it carries several viruses that harm other crops like peanuts and alfalfa.
"When I heard about the aphid, I realized we could learn a lot if we studied this outbreak as if it were a deliberate introduction," Ramaswamy said. On that hunch, he started phoning and visiting K-State colleagues, talking about a project with national security implications.
His collaborators are insect experts, science librarians and modern-day mapmakers. Ramaswamy explained: "We were tackling a complex puzzle: we wanted to see if we could determine how fast the aphid moves, where it's been; then if we could predict where it's going throughout the country, and, finally, by looking at the data could we work backwards to determine its point of entry."